95 2. Surface geophysical methods The safety of the Callovo-Oxfordian argillaceous rock (Cox) storage in the eastern Paris Basin is the major concern of the French National Radioactive Waste Management Agency (Andra). Extensive research on the clay sealing and healing properties as well as on the best way to characterize them on site have been conducted for over 20 years now. High resolution 3D seismic data have been acquired on a 30km2 underground zone, known as a zone of interest for in-depth reconnaissance (ZIRA), in the vicinity of 3 exploration drillholes. Figure 2.30a shows a view of the geological model of the site and the location map of the 3D seismic survey. The seismic processing sequence is basically a pre stack time migration and an elastic inversion of the 3D block in time (Mari and Yven, 2019). Figures 2.30b to 2.30d shows the PSTM section, the Ip and Is impedance sections obtained for the in-line IL405. (a) (b) (c) (d) Figure 2.30 3D pre stack time migration and elastic inversion of the IL 405 profile. (a) Geological model and location map of the 3D survey, (b) PSTM sections, (c) Ip section, (d) Is section. After Mari and Yven (2019), (Andra document).
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